The government-sanctioned Shiite militia forces known as the Popular Mobilization Units launched an operation to retake a small village just south of Sinjar on Friday.

Inside Mosul Iraqi forces backed by the U.S.-led coalition are slowly closing in on a small cluster of neighborhoods in the city's west held by the extremist group.

The operation to retake Mosul was launched in October, the city's east was declared liberated in January and Iraqi forces launched the operation to retake the west the following month.

The U.S.-led coalition does not provide air cover for operation led by the Popular Mobilization Units.

The last time an Iraqi helicopter was shot down was in April, and the crash killed both pilots. In addition to coalition air support, Iraqi air force and army aircraft conduct regular strike operations over the city to support police and special forces units battling IS.